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In experimental studies, single-wave mode and two counter-rotating wave mode are often observed in rotating detonation combustors. To investigate the mechanism behind different propagation modes, high-resolution numerical simulations of two-dimensional detonation in hydrogen/air mixtures are conducted by solving the reactive Navier–Stokes equations with a detailed chemical mechanism. The numerical results show that the occurrence of the dual-wave detonation propagation mode is positively influenced by an increase in both the channel width and the initial pressure. The dual-wave modes are observed when increasing the channel width, and it is found that the dual-wave modes are caused by increasing the residual premixed gas height near the inner wall. When increasing the initial pressure, the initial peak detonation heat release increases, which leads to the increase in the hot spot intensity formed, and it is found that the dual-wave modes are mainly caused by the interactions between the initial detonation wave and the inner wall. However, the initial equivalent ratio appears to have a relatively minor impact on the detonation propagation mode due to a relatively narrow range variation of physical properties. The peak heat release rate exerts a greater influence on the change of the propagation mode than the induction time does through a wider range test on rotating detonation engines' working condition. Moreover, the velocities and the cell sizes of detonation waves propagating in different directions with different channel widths are also analyzed, revealing that the characteristics of the detonation waves propagating in different directions are nearly the same. [ABSTRACT FROM AUTHOR]

During the production of underground engineering, investigating the mechanical behaviors of rock materials after high temperature damage is of great importance for controlling the stability of the underground structure. In this paper, for revealing the deformation and energy evolution laws of rock materials after high temperature damage under cyclic loading, a series of uniaxial compressive and cyclic loading experiments were conducted on sandstone after various high temperature damages, i.e., 200, 300, 400, 500, 600, 700, 800, and 900°C, to study the effect of high temperature on primary wave velocity, microstructure, deformation, strength, energy, etc. It can be observed that the primary wave velocity and microstructure weakened seriously with the development of high temperature damage and the uniaxial compressive strength of samples increases toward the maximum value with a high temperature damage of 300°C and then decreases gradually. The energy proportion index was established to characterize the influence of high temperature damage and cyclic stress levels on energy evolution laws of samples. With an increase in temperature, compared with input energy, elastic strain energy proportion decreases and dissipated energy proportion rises up, which indicate that the property of samples transforms from elasticity to plasticity. Finally, the variation laws between the burst tendency of the sample and high temperature damage were well described by presenting the average elastic energy index, which provides references for studying failure characteristics of rock materials. [ABSTRACT FROM AUTHOR]

In this paper, the weighting techniques are directly acted on traditional 1D sinusoidal electromagnetic bandgap (EBG) structures. The proposed 1D weighted EBG band-stop filter is theoretically designed by using coupled-mode theory, and the coupling coefficient amplitudes of the 1D sinusoidal EBG structure are directly weighted using window functions. The passband ripple, reflected sidelobes, and bandwidth of the band-stop filter are improved using weighted window functions, and the bandgap depth is adjusted by changing the amplitude factor of weighting functions. For validation, the fabrication and measurements have also been done for the proposed filter. The measurement and simulation results have a close match, and the design concept is verified. [ABSTRACT FROM AUTHOR]